The county's deserts and foothills could get a half-inch or more of rain this weekend from Ivo, a system that's expected to reach tropical storm status today off the Pacific coast of Mexico. Remnants from the system also could bring scattered showers and thunderstorms to the coast and nearby valleys, where seasonal rainfall is running at half its normal levels. The low pressure system off the California coast is circulating counter-clockwise, drawing sub-tropical moisture into the region.

Convection over the desert was visible Wednesday and Thursday from San Diego. Gary Robbins

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Convection over the desert was visible Wednesday and Thursday from San Diego.

The National Weather Service says Ivo is expected to "move north along the southern Baja coast. It will die about halfway up the peninsula, but the remnant moisture will pour into Southern California on Sunday. Temperatures will be dampened by lots of clouds and precipitation. But it will feel plenty humid. On Monday, the moisture wave begins to depart the region toward the northeast and the chances of precipitation will follow that path."

Daytime highs will be below seasonal levels Saturday in San Diego, but reach normal on Sunday, or close to it. Many inland areas -- particularly places like Alpine -- will be in the upper 80s and 90s.

Adam Wright, chief forecaster at Solspot.com, says that San Diego County will not receive a bump in surf from Ivo, but a swell out of the southeast could help Orange County's south-facing beaches by late in the weekend. Local surf will be in the 2' to 3' range, and sea surface temperatures are running 66-69 degrees along the entire coast.

Ticker: San Diego's Lindbergh Field has recorded 3.38'' of rain since January 1st. That's 3.46'' below average.